Question

A person travels by car from one city to another. He drives for 30.0 min at 80.0 km/h, 12.0 min at 105 km/h, and 45.0 min at 40.0 km/h, and he spends 15.0 min eating lunch and buying gas. What is the average speed for the trip?

Answer 1

53.53 km/h

Step-by-step explanation:

Given that the person drives for 30.0 min at 80.0 km/h, 12.0 min at 105 km/h, and 45.0 min at 40.0 km/h, and he spends 15.0 min eating lunch and buying gas.

So, the total time to complete the journey is

t=30+12+45+15=102 min

`=(102)/(60)=1.7` hours

As distance=(speed)x(time), so

the distance covered in 30 minutes with a speed of 80 km/h

`d_1=80 * (30)/(60)=40` km.

The distance covered in 12 minutes with a speed of 105 km/h

`d_2=105 * (12)/(60)=21 km`.

The distance covered in 45 minutes with a speed of 40 km/h

`d_3=40 * (45)/(60)=30 km`.

So, to the total distance covered is

`d=d_1+d_2+d_3`

`=40+21+30=91 km`

As the average speed = (Total distance covered)/(Total time taken)

So, the average speed for the whole journey

`=(d)/(t)`

`=(91)/(1.7)= 53.53 km/h`.

Hence, the average speed for the trip is 53.53 km/h.